Physicists Don’t Know the Mass of a Neutrino, But Now They Know it’s No Larger Than 1 Electron Volt

The NUmI (Neutrinos from the Main Injector) horn at Fermilab, which fires protons that degrade into neutrinos. (Image: Caltech)

The Standard Model of Particle Physics is one of science’s most impressive feats. It’s a rigorous, precise effort to understand and describe three of the four fundamental forces of the Universe: the electromagnetic force, the strong nuclear force, and the weak nuclear force. Gravity is absent because so far, fitting it into the Standard Model has been extremely challenging.

But there are some holes in the Standard Model, and one of them involves the mass of the neutrino.

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